Photovoltaic device with passivated contact and corresponding method of manufacture

Abstract

Disclosed is a photovoltaic device including: —a silicon substrate; —a first tunnel layer situated upon at least a first side of the silicon substrate; —a first polycrystalline silicon-based capping layer situated upon the first tunnel layer; and —a second tunnel layer situated upon substantially the entirety of the first polycrystalline silicon-based capping layer. The photovoltaic device further includes: —a second polycrystalline silicon-based capping layer situated upon predetermined zones of the second tunnel layer, areas of the second tunnel layer situated outside of the predetermined zones being free of the second polycrystalline silicon-based capping layer; and —a metal contact situated upon at least part of the second polycrystalline silicon-based capping layer.

The invention claimed is: 
     
       1. Photovoltaic device comprising:
 a silicon substrate; 
 a first tunnel layer situated upon at least a first side of said silicon substrate; 
 a first polycrystalline silicon-based capping layer situated upon said first tunnel layer; 
 a second tunnel layer situated upon substantially the entirety of said first polycrystalline silicon-based capping layer; 
 
       wherein said photovoltaic device further comprises:
 a second polycrystalline silicon-based capping layer situated upon predetermined zones of said second tunnel layer, areas of said second tunnel layer situated outside of said predetermined zones being free of said second polycrystalline silicon-based capping layer; and 
 a metal contact situated upon at least part of said second polycrystalline silicon-based capping layer. 
 
     
     
       2. The photovoltaic device according to  claim 1 , wherein said first tunnel layer is made of a dielectric material, and said second tunnel layer is made of a dielectric material or a semiconductor alloy. 
     
     
       3. The photovoltaic device according to  claim 1 , wherein at least one of said first polycrystalline silicon-based capping layer and said second polycrystalline silicon-based capping layer is made of polycrystalline silicon with or without hydrogenation. 
     
     
       4. The photovoltaic device according to  claim 1 , wherein said second polycrystalline silicon-based capping layer and said first polycrystalline silicon-based capping layer are doped, and wherein said second polycrystalline silicon-based capping layer has the same dopant type as said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       5. The photovoltaic device according to  claim 4 , wherein said second polycrystalline silicon-based capping layer has a dopant concentration which is greater than that of said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       6. The photovoltaic device according to  claim 1 , wherein said metal contact is of silver, AgAl, aluminium or copper paste. 
     
     
       7. The photovoltaic device according to  claim 1 , wherein:
 said first tunnel layer has a thickness of between 0.5 nm and 5 nm; and/or 
 said first polycrystalline silicon-based capping layer has a thickness of between 5 nm and 100 nm; and/or 
 said second tunnel layer has a thickness of between 0.5 nm and 5 nm; and/or 
 said second polycrystalline silicon-based capping layer has a thickness of greater than 5 nm. 
 
     
     
       8. Method of manufacturing a photovoltaic device, comprising steps of:
 a) providing a silicon substrate; 
 b) forming a first tunnel layer situated upon at least a first side of said silicon substrate; 
 c) forming a first polycrystalline silicon-based capping layer upon said first layer; 
 d) forming a second tunnel layer upon substantially the entirety of said first polycrystalline silicon-based capping layer; 
 
       wherein said method further comprises:
 e) forming a second polycrystalline silicon-based passivation layer upon said second tunnel layer in predetermined zones, areas of said second tunnel layer situated outside of said predetermined zones being free of said second polycrystalline silicon-based capping layer; and 
 f) forming a metal contact upon at least part of said second polycrystalline silicon-based capping layer. 
 
     
     
       9. The method according to  claim 8 , wherein step e) further comprises substeps of:
 e1) forming said second polycrystalline silicon-based capping layer upon substantially the entirety of said second tunnel layer, subsequently 
 e2) selectively removing said second polycrystalline silicon-based capping layer outside of said predetermined zones so as to expose said second tunnel layer in areas outside of said predetermined zones. 
 
     
     
       10. The method according to  claim 8 , wherein said first tunnel layer is made of a dielectric material, and said second tunnel layer is made of a dielectric material or a semiconductor alloy. 
     
     
       11. The method according to  claim 8 , wherein at least one of said first polycrystalline silicon-based capping layer and said second polycrystalline silicon-based capping layer is made of polycrystalline silicon. 
     
     
       12. Method according to  claim 8 , wherein said second polycrystalline silicon-based capping layer and said first polycrystalline silicon-based capping layer are doped, and wherein said second polycrystalline silicon-based capping layer has the same dopant type as said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       13. The method according to  claim 12 , wherein said second polycrystalline silicon-based capping layer has a dopant concentration which is greater than that of said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       14. The method according to  claim 8 , wherein said metal contact is of silver, AgAl, aluminium or copper paste. 
     
     
       15. The method according to  claim 8 , wherein:
 said first tunnel layer has a thickness of between 0.5 nm and 5 nm; and/or 
 said first polycrystalline silicon-based capping layer has a thickness of between 5 nm and 100 nm; and/or 
 said second tunnel layer has a thickness of between 0.5 nm and 5 nm; and/or 
 said second polycrystalline silicon-based capping layer has a thickness of greater than 5 nm. 
 
     
     
       16. The photovoltaic device according to  claim 2 , wherein at least one of said first polycrystalline silicon-based capping layer and said second polycrystalline silicon-based capping layer is made of polycrystalline silicon with or without hydrogenation. 
     
     
       17. The photovoltaic device according to  claim 2 , wherein said second polycrystalline silicon-based capping layer and said first polycrystalline silicon-based capping layer are doped, and wherein said second polycrystalline silicon-based capping layer has the same dopant type as said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       18. The photovoltaic device according to  claim 3 , wherein said second polycrystalline silicon-based capping layer and said first polycrystalline silicon-based capping layer are doped, and wherein said second polycrystalline silicon-based capping layer has the same dopant type as said first polycrystalline silicon-based capping layer in the corresponding predetermined zone. 
     
     
       19. The photovoltaic device according to  claim 2 , wherein said metal contact is of silver, AgAl, aluminium or copper paste. 
     
     
       20. The photovoltaic device according to  claim 3 , wherein said metal contact is of silver, AgAl, aluminium or copper paste.